1. Field of the Invention
This invention relates to devices and methods for manual application of chemical substances to selected plants at specific locations thereon.
2. Background Art
Conventional methods of applying chemical substances to vegetation include spraying, sprinkling or sowing solutions or mixtures of the chemicals on the whole plant area. Such "broadcast" methods reduce the desired concentrations on the specific plants to be treated, increase the cost of the chemicals, and subject vegetation far removed from the treatment area to the chemicals due to "drift", "vaporization," "translocation," or "leaching".
To avoid these difficulties associated with the broadcast methods, the individual application of chemicals has been made by hand to selected plants. Selective application has permitted the use of highly potent by relatively safe non-selective herbicides for the control of weeds and other undesirable vegetation. A preferred kind of non-selective herbicide is a 41% solution of isopropylamine salt of N-(phosphonomethyl) glicine, as further described in U.S. Pat. Nos. 3,799,758 and 4,405,531 and sold under the trademark "ROUNDUP" by the Monsanto Company, Agricultural Products Div., St. Louis, Missouri 63167.
Weed control at golf courses has been an especially difficult task. As described by Steve M. Batten in his article "Those Irrepressible, Incredibly, Impossible Grassy Weeds-" USGA Green Section RECORD, September/October 1984 pp. 1-4, millions of dollars are spent annually and thousands of hours are devoted to golf course weed control. Weed control methods include scalping, deep-set vertical mowing, turning off irrigation, hand removal, excavation, and starvation by eliminating normal fertilization. Spot application of non-selective herbicide is typically made with hand-held sprayers, plastic squeeze bottles, hypodermic syringes, and paint brushes.
Another known method of spot applications is to use a rubber glove having an outer absorbent mitten or sponge which can be dipped in a container of herbicide solution and then wiped against undesired vegetation.
Still another method of manually applying herbicide to selected plants is to use an applicator of the kind having a handle carrying a sponge at the lower end of the handle. In one such kind of applicator, advertised under the trademark "WALK A WICK", an applicator bottle containing a supply of herbicide solution is mounted on the upper end of the handle and is provided with a calibration valve for metering a regulated flow of herbicide from the applicator bottle to the sponge. A particular version designated as "Model 200 Pro Applicator" has a cylindrical sponge which may be provided with an optional shield.
While these methods and devices are suitable for applying herbicide to a rather large area of plants by sweeping the applicator or sponge across the undesired vegetation, or to isolated plants by blotting them with the tip of the applicator or sponge, considerable care must be taken to avoid contact with desirable grasses, plants or shrubs as injury may occur. Therefore, these devices are not especially suited for applying herbicide to weeds that are surrounded by and in close proximity to desired plants. Also, the exposed foliage of many kinds of plants is not sufficiently stiff to receive a desired amount of herbicide merely contact or wiping against an applicator or sponge.